This box is 50% PLUS 100px wide (50px + 50px).

This box is 25% PLUS 200px wide (100px + 100px).

This box is 15% PLUS 300px wide (150px + 150px).

This box is 50% PLUS 200px wide (100px + 100px).

This box is 25% PLUS 200px wide (0px + 200px).

This box is 15% PLUS 250px wide (250px + 0px).

This box is 50% wide with a 50px border and contains another box which has the same TOTAL width

This box is 100% PLUS 100px wide (50px + 50px).

This box will track the outer box to maintain the same width including the fixed pixel size borders,